data-structures/src/com/leetcode/problems/medium/InsertDeleteGetRandom_o_1.java at master · neerajjain92/data-structures · GitHub

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package com.leetcode.problems.medium;

import java.util.*;

/**
 * @author neeraj on 12/10/19
 * Copyright (c) 2019, data-structures.
 * All rights reserved.
 */
public class InsertDeleteGetRandom_o_1 {

    public static void main(String[] args) {
        RandomizedSet obj = new RandomizedSet();
        boolean param_1 = obj.insert(1);
        boolean param_2 = obj.remove(2);
        boolean param_4 = obj.insert(2);
        int param_3 = obj.getRandom();
        System.out.println(param_3);
        boolean param_5 = obj.remove(1);
        boolean param_6 = obj.remove(2);
        int param_7 = obj.getRandom();
        System.out.println(param_7);
    }


    static class RandomizedSet {

        /**
         * Initialize your data structure here.
         */
        List<Integer> data;
        Map<Integer, Integer> dataToIndexMap;
        Random random;

        public RandomizedSet() {
            random = new Random();
            data = new ArrayList<>();
            dataToIndexMap = new HashMap<>();
        }

        /**
         * Inserts a value to the set. Returns true if the set did not already contain the specified element.
         */
        public boolean insert(int val) {
            if (dataToIndexMap.containsKey(val)) return false;
            data.add(val); // append to last in the list

            // Point to the node in list from hashMap
            dataToIndexMap.put(val, data.size() - 1);
            return true;
        }

        /**
         * Removes a value from the set. Returns true if the set contained the specified element.
         */
        public boolean remove(int val) {
            if (!dataToIndexMap.containsKey(val)) return false;

            int index = dataToIndexMap.get(val);

            if (index < data.size() - 1) {
                int lastItem = data.get(data.size() - 1);
                data.set(index, lastItem);
                dataToIndexMap.put(lastItem, index);
            }
            data.remove(data.size() - 1);
            dataToIndexMap.remove(val);
            return true;

        }

        /**
         * Get a random element from the set.
         */
        public int getRandom() {
            int randomValue = random.nextInt(data.size());
            return data.get(randomValue); // O(1) index based access.
        }
    }

/**
 * Your RandomizedSet object will be instantiated and called as such:
 * RandomizedSet obj = new RandomizedSet();
 * boolean param_1 = obj.insert(val);
 * boolean param_2 = obj.remove(val);
 * int param_3 = obj.getRandom();
 */


//    public static class RandomizedSet {
//        Map<Integer, Integer> valPositionMap;
//        List<Integer> allValues;
//
//        /**
//         * Initialize your data structure here.
//         */
//        public RandomizedSet() {
//            valPositionMap = new HashMap<>();
//            allValues = new ArrayList<>();
//        }
//
//        /**
//         * Inserts a value to the set. Returns true if the set did not already contain the specified element.
//         */
//        public boolean insert(int val) {
//            if (!valPositionMap.containsKey(val)) {
//                allValues.add(val);
//                valPositionMap.put(val, allValues.size() - 1);
//                return true;
//            } else {
//                return false;
//            }
//        }
//
//        /**
//         * Removes a value from the set. Returns true if the set contained the specified element.
//         */
//        public boolean remove(int val) {
//            if (valPositionMap.containsKey(val)) {
//                int index = valPositionMap.get(val);
//
//                // If this is not the last item
//                if (index < allValues.size() - 1) {
//                    // Swap the val with the last item in map
//                    int lastItem = allValues.get(allValues.size() - 1);
//                    allValues.set(index, lastItem);
//                    valPositionMap.put(lastItem, index);
//                }
//                allValues.remove(allValues.size() - 1);
//                valPositionMap.remove(val);
//                return true;
//            } else {
//                return false;
//            }
//        }
//
//        /**
//         * Get a random element from the set.
//         */
//        public int getRandom() {
//            return allValues.get(new Random().nextInt(allValues.size()));
//        }
//    }
}